Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d0c879bc authored by Daniel Norman's avatar Daniel Norman
Browse files

Ensure the MagThumbnail view is always inflated on the main thread. 

I believe this is one cause of deadlock, in addition to going against
best practice that View inflation should only run on the main thread.

At the same time:
(1a) android.bg thread: FullScreenMagnificationController locks
    A11yManagerService.mLock when calling onUserStateChanged.
(1b) AudioService thread: AudioService locks A11yManager.mLock
    when checking A11yManager.isTouchExplorationEnabled

Then, at the same time:
(2a) android.bg thread: FullScreenMagnificationController inflates
    MagnificationThumbnail which is waiting to lock A11yManager.mLock
    in order to check A11yManager.isEnabled
(2b) AudioService thread: A11yManager.isTouchExplorationEnabled is
    waiting to lock A11yManagerService.mLock in order to register the
    A11yManager client.

By posting the View inflation to the system_server main thread we allow
1a to release its A11yManagerService.mLock so that 2b can proceed, releasing A11yManager.mLock (locked in 1b) so that 2a can proceed.

Bug: 287127293
Test: Log the thread ID/label of the mag thumbnail layout inflation,
      ensure it is the main thread
Change-Id: Ibe2574e5c83729d749befd343299fb26e3036037
parent 442bbb16

services/accessibility/java/com/android/server/accessibility/magnification/MagnificationThumbnail.java

+10 −5
Original line number Diff line number Diff line
@@ -56,9 +56,9 @@ public class MagnificationThumbnail { 
    private final Handler mHandler;



    @VisibleForTesting

    public final FrameLayout mThumbnailLayout;

    public FrameLayout mThumbnailLayout;



    private final View mThumbnailView;

    private View mThumbnailView;

    private int mThumbnailWidth;

    private int mThumbnailHeight;
@@ -79,13 +79,18 @@ public class MagnificationThumbnail { 
        mWindowManager = windowManager;

        mHandler = handler;

        mWindowBounds =  mWindowManager.getCurrentWindowMetrics().getBounds();

        mBackgroundParams = createLayoutParams();

        mThumbnailWidth = 0;

        mThumbnailHeight = 0;

        mHandler.post(this::createThumbnailLayout);

    }



    @MainThread

    private void createThumbnailLayout() {

        mThumbnailLayout = (FrameLayout) LayoutInflater.from(mContext)

                .inflate(R.layout.thumbnail_background_view, /* root: */ null);

        mThumbnailView =

                mThumbnailLayout.findViewById(R.id.accessibility_magnification_thumbnail_view);

        mBackgroundParams = createLayoutParams();

        mThumbnailWidth = 0;

        mThumbnailHeight = 0;

    }



    /**